secret electricity?

[lozz]

iwonder if this is true or B/s ?

see video. http://www.youtube.com/watch?v=WoaLGvJkoP8

[steve_earwig]

Not-so-secret source of low current 50 volts

[markw]

You should see the HUGE banks of batteries that are (were) installed in telephone exchanges (at least, in the older type exchange before all the electro-mechanical stuff got ripped out) and they're there to keep the phone system up and running in the event of a power outage.
I'm not in the same job anymore so don't get to visit exchanges, so I'd imagine that as most, if not all, are now converted to digital, the need for huge battery capacity has been removed.
Yes, there's a dc voltage present on the incoming line but whether you could do more than get a few leds to come on like in the vid would be debateable....


PS if you go ahead and do something like this guy did....don't be moaning when you're Broadband goes belly up!

[steve_earwig]

You too huh? Just batteries? You missed out on the huge generators, bluddy great diesel train engines These days the back-up batteries are mostly in the bottom of the equipment rack and the battery rooms are just another empty room.

Yes indeed, just a few leds on a wire, rather pointless if you have a torch

[lozz]

cheers

no iwasnt going to run anything off it, iwas just curious after seeing failtube video,,

[steve_earwig]

I suppose, if you were really clever about it, you could charge up a car battery. It would take about a year though

Power cut? In the dark? Just set fire to your trousers!

[lozz]

ive actualy done that,

not trouser exactly but shell suit pants, back in the late 80s'

lesson learnt was don't stand in front of gas fire with them on,

[Puggy2]

The circuit could be modified to make 5volts and then could be a very good USB charger for pnones etc. Iain

[Puggy2]

And here's another one http://www.youtube.com/watch?v=8GAacxGiV4A

[mjb]

You too huh? Just batteries? You missed out on the huge generators, bluddy great diesel train engines These days the back-up batteries are mostly in the bottom of the equipment rack and the battery rooms are just another empty room.

Nah, you never get rackmount UPSs in decent datacentres/exchanges because of inefficiency and safety. It's much more cost effective to have the honking great UPS system before the power distribution - just enough to keep going while the generators kick in, and nowadays power is at a premium (not rare to see whole racks with only 6-10U occupied due to ridiculously low power constraints) so the efficiency of this method makes it more suitable. Also, UPSs can cause massive upstream loads - imagine a room with a few hundred 3+kVA units deciding to do self-tests at the same time...

Crucially though, it also means you have one point (or common set of points) at which power can be isolated via the big red button on the wall. If something goes up in smoke, you need to be able to kill power to everything in a room which is why colo centres universally prohibit the use of UPSs in racks. Not to mention that batteries themselves are a massive fire risk...

Having said that, I know Google use custom-designed hardware with a mini-UPS per server. God knows how they manage that

[steve_earwig]

I get what you're saying but why are all the battery rooms empty? I get that a Strowger needed a hell of a lot more power than a system X/Y/whatever but even then there wasn't a single cell left in a lot of the exchanges I used to work in. Unless they've been relocated to an equipment floor somewhere but again, eggs in one basket.

[mjb]

I get what you're saying but why are all the battery rooms empty? I get that a Strowger needed a hell of a lot more power than a system X/Y/whatever but even then there wasn't a single cell left in a lot of the exchanges I used to work in. Unless they've been relocated to an equipment floor somewhere but again, eggs in one basket.

I think nowadays you can get more than 100kVA of batteries in a cabinet roughly the size of a server rack (19" front, 1200mm deep) which can look not too dissimilar to server racks or PDUs, so you may not have noticed them. Additionally, modern kit really does use a tiny fraction of the power older kit did - when I worked for a small telco, they replaced a large installation of bungalow-sized DMS100 switches with one small room's worth of "something", and that was well over 10 years ago. I imagine it could be replaced with half a cab's worth nowadays...

[steve_earwig]

Burgered if I know, I'm just a jumper monkey. My bro would know, he's transmission but now they have him doing system x & y, no training mind, just push it into his task list and... in at the deep end